Method for manufacturing a polymer molecular film for photo-electronic device

ABSTRACT

The present invention provides a polymer molecular film, a photo-electronic element comprising the same and method for manufacturing the same. The polymer molecular film of the invention is formed via a deformation process on a substrate. Particularly, the polymer molecular film includes a plurality of conjugated polymers, therein at least one of the conjugated polymers has a stretched molecular structure. As a result, the photo-electronic element having said polymer molecular film performs with good lighting or power generating efficiency.

FIELD OF THE INVENTION

This invention relates to a polymer molecular film, a photo-electronicelement and a method for manufacturing the same.

BACKGROUND OF THE INVENTION

Polymer is constructed by repetitive chemical bonding between low molarmass molecules. The common structures can be linear, network, orbranched. Although conventional polymeric materials are generallyinsulators, polymers with conjugated chain structures are capable toconduct electricity by transport of pi electrons. Particularly, with theprocedures of redox reactions, the conductivity of conjugated polymerscan reach the levels of doped inorganic semiconductors or someconductors. This unique property, when combined with other importantadvantages such as low material cost, simple fabrication processes,compatibility with large area manufacturing, light weights, and bendablemechanical properties, has made conjugated polymers emerging as thevital candidate for next generation optoelectronics. For example, PLEDs(polymer light emitting diode) are the application that is widelystudied. In short, conjugated polymers are used as a kind of lightemitting material, which in turn is applied between positive electrodesand negative electrodes to form light emitting films. When forward biasis applied, holes are injected into the polymer molecular film from thepositive electrodes and enter valence band to become positive polarons.Moreover, electrons are injected from negative electrodes and enter aconducting band to become negative polarons. And the two polarons movein the opposing directions to be combined to emit fluorescence (visiblelight).

Polymer LEDs can become polymer semiconductor laser with proper designand manufacturing process. The operation principle of the polymersemiconductor laser is generally similar to that of polymer LEDs, butthat the resonant cavity structure is particularly introduced andpopulation inversion is achieved by suitable electron levels, so thatwhen the light is transmitted in the semiconductor polymer layer, energygap wavelength photons are stimulated to emit high intensity coherentlight.

For example, the elements having the similar structure to theaforementioned structures can also be used to generate electrical power,such as using that to manufacture an electrical power generating elementusing solar energy. Using the energy of the photons to separate theelectrons and the holes. After being separated, the holes move towardspositive electrodes, and the electrons move towards negative electrodesso as to form charges needed by external circuits, and the photonicenergy can be transformed into electrical energy.

No matter it's the aforementioned light emitting or electrical powergenerating elements, better efficiency is needed for increasing theapplicability thereof.

SUMMARY OF THE INVENTION

Therefore, the first objective of this invention is to provide a polymermolecular film. Particularly, the polymer molecular film has higherlight-emitting/power-generating efficiency, which can be widely appliedin manufacturing all kinds of photo-electronic elements.

According to an embodiment, the polymer molecular film is formed on asubstrate through a deformation process. Particularly, the polymermolecular films comprise a plurality of conjugated polymers, wherein atleast one of the plurality of conjugated polymers has a stretchedmolecular structure.

The second objective of this invention is to provide a method formanufacturing aforementioned polymer molecular films.

According an embodiment, the method includes the following steps: First,applying a conjugated polymeric material on a substrate to form apolymeric material layer; then, un-stabilizing the polymeric materiallayer to form a polymer molecular film; wherein, at least one conjugatedpolymer of the polymer molecular films has a stretched molecularstructure.

In an embodiment, the step of un-stabilizing the polymeric materiallayer to form the polymer molecular film further comprises: disposingthe polymeric material layer in vapor of a solvent.

In another embodiment, the step of unstablizing the polymeric materiallayer to form the polymer molecular film further comprises: heating thepolymeric material layer until the temperature is higher than glasstransition temperature of the conjugated polymeric materials.

The third objective of this invention is to provide a photo-electronicelement, comprising the aforementioned polymer molecular films, so thatthe photo-electronic element has higher light-emitting/power-generatingefficiency.

According to an embodiment, the photo-electronic element comprises asubstrate, the polymer molecular film and a protection layer. Thesubstrate and the protection layer can also be the transporting layerfor the electrodes, or electrons and holes. The polymer molecular filmis formed on the substrate, and the protection layer is formed on thepolymer molecular film to prevent the polymer molecular film fromoxidation or wear.

The fourth objective of this invention is to provide the method formanufacturing the aforementioned photo-electronic elements.

According to an embodiment, the steps of the method include thefollowing: First, preparing a substrate, then applying a conjugatedpolymeric material on the substrate to form a polymeric material layer,and then un-stabilizing the polymeric material layer to form the polymermolecular film; wherein, at least one conjugated polymer in the polymermolecular films has a stretched molecular structure.

The advantages and the spirits of this invention can be furtherunderstood with the following description and the appended drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a flow chart of an exemplary polymer molecular filmmanufacturing method in accordance with embodiments of this invention.

FIG. 2A illustrates an exemplary substrate in accordance withembodiments of this invention.

FIG. 2B illustrates an exemplary polymeric material layer in accordancewith embodiments of this invention.

FIG. 2C illustrates an exemplary polymer molecular film in accordancewith embodiments of this invention.

FIG. 3 illustrates an exemplary flow chart of the polymer molecular filmmanufacturing method in accordance with embodiments of this invention.

FIG. 4 illustrates an exemplary polymer molecular film in accordancewith embodiments of this invention correspond to the photoluminancespectra of different dewetting time during dewetting process.

FIG. 5 illustrates the cross-sectional view of an exemplary lightemitting element in accordance with embodiments of this invention.

DETAILED DESCRIPTION OF THE INVENTION

This invention provides a sort of polymer molecular film,photo-electronic element, and the method of manufacturing the polymermolecular film and the photo-electronic element. The followings are theembodiment and the practical applications of the invention, and thosewill be further described to better explain the characteristics, spiritsand advantages of this invention.

Please refer to FIG. 1 and FIG. 2A to FIG. 2C. FIG. 1 illustrates theflow chart of the polymer molecular film manufacturing method of anembodiment of this invention. FIG. 2A illustrates the substrate 10formed by Step S50 in FIG. 1; FIG. 2B illustrates the polymeric materiallayer 12 formed by Step S52 in FIG. 1; and FIG. 2C illustrates thepolymer molecular film 14 formed by Step S54 in FIG. 1. As illustrated,the manufacturing method according to this embodiment includes thefollowing steps:

Step S50, preparing a substrate 10, for example but not limited to, aglass substrate, Indium Tin Oxides (ITO), etc.

Step S52, applying conjugated polymeric material to form a polymericmaterial layer 12 on the substrate 10. In practice, the conjugatedpolymeric material is applied to the substrate 10 by spin coating orother proper means. In practice, the thickness of the polymeric materiallayer 12 is less than 300 nm, such as 200 nm, 100 nm, 50 nm, andpreferably less than 30 nm. In practice, the conjugated polymericmaterial can be a single polymer or several polymers composed of a sortof mixture or copolymer. The conjugated polymer includes, but notlimited to, poly[1-methoxy-4-(2′-ethyl-hexyloxy)-2,5-phenylenevinylene], MEH-PPV, polythiophene or polyphenylene, etc. Moreover, inpractice, the conjugated polymeric material may include othernonconjugated polymeric materials, such as polystyrene (PS), as well asother proper additives.

Step S54, heating the polymeric material layer 12 such that thetemperature of the polymeric material layer 12 is higher than the glasstransition temperature (Tg) so as to allow the polymeric material layer12 to deform to the polymer molecular film 14.q

As illustrated by FIG. 2C, the polymer molecular film 14 has a pluralityof protrusion areas 140 and, possibly, a plurality of serial indentationareas 142. Particularly, at least one conjugated polymer of theplurality of indentation areas 142 has a stretched molecular structurein unilateral direction. Furthermore, in practice, the distance betweenthe surface 1420 of the indentation area 142 and the surface 102 of thesubstrate 10 is less than 100 nm; for example, between 0.5 nm and 50 nm,and preferably less than 20 nm. In practice, by surface treatment to thesubstrate surface, the thickness of the indentation areas can becontrolled.

In practice, Step S54 is the conventional dewetting step. This step candrag conjugated polymers on the surface of the substrate to form a filmhaving stretched molecular structures, and the originally flat polymericmaterial layer is now fractured to form droplets (same as the protrusionarea described above). Because the conjugated polymers are stretched,the conjugated polymeric chains are less likely to be bent, so that thecharges (including electrons and holes) can move freely on the polymerchains without being trapped by polymer chains and therefore, it iseasier to emit light/generate power. After the preliminary experiment,the luminous efficiency of the polymer molecular film after, beingdewetted has at least one order of magnitude higher than that of thepolymer molecular film before being dewetted.

Please refer to FIG. 3. FIG. 3 illustrates a flow chart of the polymermolecular film manufacturing method of a different embodiment of thisinvention. As illustrated by FIG. 3, Step S54 in FIG. 1 can be replacedby Step S56 which proceeds the followings: under room temperature,disposing the polymeric material layer in the vapor of a certain solvent(such as Toluene, p-toluene, Tetrahydrofuran (THF), methanol or otherproper solvents), such that the polymeric material layer 12 isun-stabilized and deformed to become the polymer molecular film 14.

Moreover, in practice, the aforementioned Step S52 and S54/S56 can berepetitively implemented to form multiple polymer molecular film layersto increase light-emitting/power-generating efficiency. Moreover, inpractice, the method of this invention can also include the followingsteps: removing the parts of the protrusion areas which are higher thanthe indentation areas, such that the polymer molecular film has thesurface that is generally flat. By doing this, the situation that thelight emitted from the indentation area is affected by the protrusionareas can be avoided. On the contrary, when Step S52 and S54 areimplemented repetitively to form multiple polymer molecular film layers,the protrusion areas may be remained, so as to help fix the bondingbetween the films.

Please refer to FIG. 4. FIG. 4 illustrates polymer molecular films of anembodiment of this invention during dewetting process, corresponding tothe photoluminance spectra in different dewetting time. In thisembodiment, luminous polymeric material MEH-PPV is spin coated on asilicone oxide to form a film with 20 nm thickness, and disposed in anenvironment of 100 degrees (° C.) of temperature for different timeperiods to implement dewetting. Moreover, FIG. 4 shows the resultsgenerated by a fluorescence spectrometer. As illustrated by the figure,when the dewetting time period is 300 minutes, the film is completelydewetted and the luminous efficiency increases 30 times to that of thefilm before dewetting.

This invention further provides method for manufacturing thephoto-electronic element having therein the aforementioned polymermolecular films. The photo-electronic element can be applied in manydifferent fields; for example, used as polymer LEDs, polymersemiconductor laser, solar cell elements, etc, but not limited tothereto.

Please refer to FIG. 5. FIG. 5 schematically illustrates thecross-sectional view of the light-emitting element of the embodiment ofthis invention. As illustrated by the figure, according to the lightemitting element 2 of this invention includes a substrate 20, a positiveelectrode 22, a hole transporting layer 24, a light emitting layer 26and a negative electrode 28.

In practice, the substrate 20 can be made of a transparent glass orother appropriate materials. The positive electrode 22 can be made of aconductive material, such as Indium oxide (ITO). The hole transportinglayer 24 can be made of conductive polymeric material(3,4-polyethylenedioxythiophene/polystyrenesulfonate blend, PEDOT/PSS).The light emitting layer 26 is made of polymer molecular film of thisinvention. Moreover, the negative electrodes 28 can be made of aluminumor other metals.

In practice, according to the photo-electronic element of this inventionapart from the aforementioned substrates and polymer molecular films, italso includes a protection layer formed on the polymer molecular film toprevent the polymer molecular film from oxidation or wear.

Moreover, the photo-electronic element of this invention can includepositive and negative electrodes respectively disposed on the substrateand the protection layer. Of course, in practice, the photo-electronicelement of this invention can also include other functional layersdepending on the situation without being limited by any specific types.

Furthermore, apart from the aformentioned designs that utilize thepositive and negative electrodes positioned across the thickness of themolecular layer or layers, a parallel version of the electrodes with thepositive and negative electrodes situated on a plane parallel to theplane of the molecular film can also be opted.

To conclude, the polymer molecular films and the photo-electronicelement of this invention increase the light-emitting/power-generatingefficiency by the indentation areas formed by stretched conjugatedpolymers. Moreover, this process can be achieved without taking muchtime and costing much money, which is highly industrially applicable.

Although this invention has been disclosed better as above by theembodiments, they are not intended to limit the scope of this invention.An ordinary skilled person in the art can make any modification andimprovements without departing from the spirit and scope of thisinvention. Therefore, the protection scope of this invention is definedby the appended claims.

What is claimed is:
 1. A method of manufacturing the photo-electronicelement, comprising the steps of: preparing a substrate; applying apolymeric material directly on the substrate to form a polymericmaterial layer which has at least one conjugated polymer, the polymericmaterial layer has light-emitting and power-generating efficiency, athickness of the polymeric material layer is less than 300 nm; andun-stabilizing the polymeric material layer by disposing the polymericmaterial layer in vapor of a solvent or heating the polymeric materiallayer to form a single polymer molecular film without being stretched byan additionally applied mechanical force; wherein, at least oneconjugated polymer of the single polymer molecular film has a stretchedmolecular structure.
 2. The method of claim 1, wherein the step ofun-stabilizing the polymeric material layer to form the single polymermolecular film further comprises: heating the polymeric material layerso that the polymeric material layer has a temperature which is higherthan the glass transition temperature of the polymeric material layer.3. The method of claim 1, wherein the single polymer molecular filmfurther comprises a plurality of protrusion areas and at least oneindentation area, and at least one conjugated polymer with the stretchedmolecular structure is located in the indentation area.
 4. The method ofclaim 3, further comprising the following steps: removing the parts ofthe protrusion areas which are higher than the indentation areas, suchthat the single polymer molecular film has the surface that is flat. 5.The method of claim 1, further comprising the following steps: forming aprotection layer on the single polymer molecular film to protect thesingle polymer molecular film.
 6. The method of claim 1, wherein thepolymer material is selected from the group consisting ofpoly[1-methoxy-4-(2′-ethyl-hexyloxy)-2,5-phenylene vinylene] (MEH-PPV),polythiophene and polyphenylene.